We will attempt to (1) permanently express different influenza A virus genes (gene complexes) in eukaryotic cells via bovine papilloma virus vectors. This system will allow us to study the functional interaction of viral proteins and to establish an effective complementation system for the isolation of novel influenza A virus mutants. A major effort will be directed towards (2) rescuing cloned viral cDNA into infectious virus. This approach would allow--for the first time--site-specific alterations in the genome of a negative strand RNA virus and the generation of specific mutants including those to be used as viral vaccine strains. We also plan to (3) explore the nucleophilic signals of the influenza A NS1 and NS2 proteins in order to arrive at an understanding of the requirements necessary for intracellular migration of these proteins. We will (4) continue structural work on influenza virus genes and plan to clone and sequence the remaining genes of an influenza C virus. Finally, (5) work will continue with respect to the precise measurements of mutation rates of influenza A, B and C viruses, and we hope to compare these values with that obtained for an RNA tumor virus. These studies should allow us to compare a fundamental genetic property among different virus classes and to correlate error rate of viral polymerases with variability of viruses in nature.